Re: [PATCH] t9300-fast-import: don't hang if background fast-import exits too early

>> > -	test_when_finished "
>> > +	test_when_finished '
>> >  		exec 8>&-; exec 9>&-;
>> > -		kill $(cat V.pid) && wait $(cat V.pid)
>> > -		true"
>> > +		kill $(cat V.sh.pid) && wait $(cat V.sh.pid)
>> > +		kill $(cat V.fi.pid) && wait $(cat V.sh.pid)
>> > +		true'
>> 
>> The original interpolates the PID of the fast-import when
>> "when-finished" program is registered, so it is OK if somebody else
>> removed V.pid file; the new one interpolates when "when-finished"
>> program is run, reading from V.??.pid, so somebody needs to make
>> sure these pid files will stay around.  I do not think it is an
>> issue as I suspect we've left it to the global clean-up procedure
>> that removes the trash directory to remove the pid file.
>
> In the original the same shell process starts 'git fast-import',
> writes its pidfile, and registers the test_when_finished commands, so
> we can be sure that the pid file is already present when the shell
> runs the $(cat V.pid) command substitutions.

> With this patch that's not the case anymore, because the background
> subshell starts 'git fast-import' and writes the pidfile, but the main
> shell process registers the test_when_finished commands.  IOW these
> two shell processes are racing, and it's possible that the
> test_when_finished command is executed before the background subshell
> can write the pidfile.  So double quotes around the block of
> test_when_finished commands are not good.